feat: add support for python3

- Use jq where possible
- Drop unused function (no usage across entire codebase nor in any github repository

Closes #3689

plugins/scheduler-docker-local/scheduler-inspect

@@ -40,7 +40,7 @@ for container in data:
     container['Config']['Env'] = env
     output.append(container)
 
-print json.dumps(data, sort_keys=True, indent=4)
+print(json.dumps(data, sort_keys=True, indent=4))
 EOF
 
   local CONTAINER_FILES="$(find "$DOKKU_ROOT/$APP" -maxdepth 1 -name "CONTAINER.*" -printf "%f\n" 2>/dev/null | sort -t . -k 2 -n | xargs)"